[vm/concurrency] Avoid allocating objects if not needed (and possibly cache objects)

Two growable arrays needed for possibly re-hashing objects when sending
messages using the snappshotter are often unused. Only create them when
needed.

When looking up message handler and calling it avoid repeated
allocations of small arrays (they can be cached savely because right
the transition stubs will copy the arguments out of those arrays).

This improves performance of high-frequency messages but small message
handlers.

Issue dart-lang/sdk#36097

Change-Id: I623aba5b29064f3a75ea294557ee153067a63d08
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/148263
Reviewed-by: Ryan Macnak <[email protected]>
Commit-Queue: Martin Kustermann <[email protected]>

Author: mkustermann

runtime/vm/dart_entry.cc

@@ -658,7 +658,12 @@ ObjectPtr DartLibraryCalls::LookupHandler(Dart_Port port_id) {
     ASSERT(!function.IsNull());
     thread->isolate()->object_store()->set_lookup_port_handler(function);
   }
-  const Array& args = Array::Handle(zone, Array::New(kNumArguments));
+  Array& args = Array::Handle(
+      zone, thread->isolate()->isolate_object_store()->dart_args_1());
+  if (args.IsNull()) {
+    args = Array::New(kNumArguments);
+    thread->isolate()->isolate_object_store()->set_dart_args_1(args);
+  }
   args.SetAt(0, Integer::Handle(zone, Integer::New(port_id)));
   const Object& result =
       Object::Handle(zone, DartEntry::InvokeFunction(function, args));
@@ -687,7 +692,12 @@ ObjectPtr DartLibraryCalls::HandleMessage(const Object& handler,
     ASSERT(!function.IsNull());
     isolate->object_store()->set_handle_message_function(function);
   }
-  const Array& args = Array::Handle(zone, Array::New(kNumArguments));
+  Array& args = Array::Handle(
+      zone, thread->isolate()->isolate_object_store()->dart_args_2());
+  if (args.IsNull()) {
+    args = Array::New(kNumArguments);
+    thread->isolate()->isolate_object_store()->set_dart_args_2(args);
+  }
   args.SetAt(0, handler);
   args.SetAt(1, message);
 #if !defined(PRODUCT)

runtime/vm/object_store.h

@@ -254,6 +254,8 @@ class ObjectPointerVisitor;
 #define ISOLATE_OBJECT_STORE_FIELD_LIST(R_, RW)                                \
   RW(UnhandledException, preallocated_unhandled_exception)                     \
   RW(StackTrace, preallocated_stack_trace)                                     \
+  RW(Array, dart_args_1)                                                       \
+  RW(Array, dart_args_2)                                                       \
   R_(GrowableObjectArray, resume_capabilities)                                 \
   R_(GrowableObjectArray, exit_listeners)                                      \
   R_(GrowableObjectArray, error_listeners)

runtime/vm/snapshot.cc

@@ -313,9 +313,6 @@ ObjectPtr SnapshotReader::ReadObject() {
   // Setup for long jump in case there is an exception while reading.
   LongJumpScope jump;
   if (setjmp(*jump.Set()) == 0) {
-    objects_to_rehash_ = GrowableObjectArray::New();
-    types_to_postprocess_ = GrowableObjectArray::New();
-
     PassiveObject& obj =
         PassiveObject::Handle(zone(), ReadObjectImpl(kAsInlinedObject));
     for (intptr_t i = 0; i < backward_references_->length(); i++) {
@@ -344,11 +341,14 @@ ObjectPtr SnapshotReader::ReadObject() {
 }
 
 void SnapshotReader::EnqueueTypePostprocessing(const AbstractType& type) {
+  if (types_to_postprocess_.IsNull()) {
+    types_to_postprocess_ = GrowableObjectArray::New();
+  }
   types_to_postprocess_.Add(type);
 }
 
 void SnapshotReader::RunDelayedTypePostprocessing() {
-  if (types_to_postprocess_.Length() == 0) {
+  if (types_to_postprocess_.IsNull()) {
     return;
   }
 
@@ -362,11 +362,14 @@ void SnapshotReader::RunDelayedTypePostprocessing() {
 }
 
 void SnapshotReader::EnqueueRehashingOfMap(const LinkedHashMap& map) {
+  if (objects_to_rehash_.IsNull()) {
+    objects_to_rehash_ = GrowableObjectArray::New();
+  }
   objects_to_rehash_.Add(map);
 }
 
 ObjectPtr SnapshotReader::RunDelayedRehashingOfMaps() {
-  if (objects_to_rehash_.Length() > 0) {
+  if (!objects_to_rehash_.IsNull()) {
     const Library& collections_lib =
         Library::Handle(zone_, Library::CollectionLibrary());
     const Function& rehashing_function = Function::Handle(
@@ -575,6 +578,9 @@ ObjectPtr SnapshotReader::ReadObjectImpl(intptr_t header_value,
 }
 
 void SnapshotReader::EnqueueRehashingOfSet(const Object& set) {
+  if (objects_to_rehash_.IsNull()) {
+    objects_to_rehash_ = GrowableObjectArray::New();
+  }
   objects_to_rehash_.Add(set);
 }